Faculty Publications
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Item Studies on nonlinear optical parameters of bis-chalcone derivatives doped polymer(Elsevier BV, 2006) Shettigar, S.; Chandrasekharan, K.; Umesh, G.; Sarojini, B.K.; Narayana, B.Two bis-chalcone derivatives, 1,5-[di(4-methoxyphenyl)]penta-1,4-dien-3-one and 1,5-[di(4-chlorophenyl)]penta-1,4-dien-3-one were synthesized. Their SHG conversion efficiencies are reported to be 6.0 and 5.0 times that of urea and hyper polarizabilities are 9.9×10-30 and 10.2×10-30 esu, respectively. The third-order nonlinear optical properties in PMMA matrix were studied by Z-scan technique using 7 ns laser pulses at 532 nm. The nonlinear refractive index ?, nonlinear absorption coefficient ?, magnitude of effective third order susceptibility ?(3) and the coupling factor ? have been investigated. The values obtained are of the order of 10-14 cm2/W, 1.2 cm/GW, 10-14 esu and 0.2, respectively, which are comparable with the values obtained in stilbazoleum like dyes. The experimental investigation also shows that they are very interesting optical limiting materials and their optical limiting behaviour is mainly due to two photon absorption phenomenon. © 2006 Elsevier Ltd. All rights reserved.Item Biodegradability of PMMA blends with some cellulose derivatives(2006) Bhat, D.K.; Muthu, M.S.High polymer blends of Polymethyl methacrylate (PMMA) with cellulose acetate (CA) and Cellulose acetate phthalate (CAP) of varying blend compositions have been prepared to study their biodegradation behavior and blend miscibility. Films of PMMA-CA, and PMMA-CAP blends have been prepared by solution casting using Acetone and Dimethyl formamide(DMF) as solvents respectively. Biodegradability of these blends has been studied by four different methods namely, soil burial test, enzymatic degradation, and degradation in phosphate buffer and activated sludge degradation followed by water absorption tests to support the degradation studies. Degradation analysis was done by weight loss method. The results of all the tests showed sufficient biodegradability of these blends. Degradability increased with the increase in CA and CAP content in the blend compositions. The miscibility of PMMA-CA and PMMA-CAP blends have been studied by solution viscometric and ultrasonic methods. The results obtained reveal that PMMA forms miscible blends with either CA or CAP in the entire composition range. Miscibility of the blends may be due to the formation of hydrogen bond between the carbonyl group of PMMA and the free hydroxyl group of CA and CAP. © Springer Science+Business Media, Inc. 2006.Item Third order nonlinear optical properties and two photon absorption in newly synthesized phenyl sydnone doped polymer(2007) Shettigar, S.; Umesh, G.; Chandrasekharan, K.; Kalluraya, B.We have investigated third order nonlinear optical properties of three newly synthesized 3-phenyl sydnones, doped into PMMA and determined both real and imaginary part of ?(3). The measurements were performed using nanosecond laser pulses at 532 nm wavelength by employing Z-Scan technique. The nonlinear refractive index is found to be of the order of 10-14 cm2/W. The magnitude of third order susceptibility is of the order of 10-13 esu. Their two photon absorption coefficient and absorption cross section have also been determined. The optical power limiting behavior of sydnone moieties doped PMMA was also investigated. The results suggest that among the three organic phenyl sydnone moieties, 2-benzylhydrazono-5-(3-p-tolylsydnone-4-yl)1,3,4,-thiadiazine doped PMMA is a promising class of nonlinear optical material due to its simple molecular structure with p-tolyl group. It also shows a very good optical limiting behaviour with a limiting threshold of 0.21 mJ/pulse. The nonlinear parameters obtained are comparable with the values obtained in stilbazolium like dye such as trans-4-[2-(pyrrl)vinyl]-1-methylpyridium iodide. Hence this material may be tailored suitably for applications such as optical power limiters, switches and modulators. © 2007 Elsevier B.V. All rights reserved.Item Studies on third-order nonlinear optical properties of chalcone derivatives in polymer host(Elsevier, 2008) Shettigar, S.; Umesh, G.; Chandrasekharan, K.; Sarojini, B.K.; Narayana, B.In this paper we present the experimental study of the third-order nonlinear optical properties of two chalcone derivatives, viz., 1-(4-methoxyphenyl)-3-(4-butyloxyphenyl)-prop-2-en-1-one and 1-(4-methoxyphenyl)-3-(4-propyloxyphenyl)-prop-2-en-1-one in PMMA host, with the prospective of reaching a compromise between good processability and high nonlinear optical properties. The nonlinear optical properties have been investigated by Z-scan technique using 7 ns laser pulses at 532 nm. The nonlinear refractive index, nonlinear absorption coefficient, magnitude of third-order susceptibility and the coupling factor have been determined. The values obtained are of the order of 10-14 cm2/W, 1 cm/GW, 10-13 esu and 0.2, respectively. The molecular second hyperpolarizability for the chalcone derivatives in polymer is of the order of 10-31 esu. Different guest/host concentrations have also been studied. The results suggest that the nonlinear properties of the chalcones have been improved when they are used as dopants in polymer matrix. The nonlinear parameters obtained are comparable with the reported values of II-VI compound semiconductors. Hence, these chalcons are a promising class of nonlinear optical dopant materials for optical device applications. © 2007 Elsevier B.V. All rights reserved.Item Nonlinear optical properties of p-(N,N-dimethylamino)dibenzylideneacetone doped polymer(2008) Kiran, A.J.; Satheesh Rai, N.; Udayakumar, D.; Chandrasekharan, K.; Kalluraya, B.; Philip, R.; Shashikala, H.D.; Vasudeva Adhikari, A.V.A bis-chalcone derivative, p-(N,N-dimethylamino) dibenzylideneacetone was synthesized. Its third-order nonlinear susceptibility was determined to be as high as 10-12 esu by employing single beam Z-scan and degenerate four wave mixing techniques using Nd:YAG 7 ns laser pulses at 532 nm. The compound was doped in to poly(methylmethacrylate) matrix and the third-order nonlinearity was investigated by using Z-scan technique. The nonlinear refractive index of the doped polymer is found to be negative, and its magnitude is of the order of 10-10 esu. The results show that the compound exhibits strong reverse saturable absorption and a good optical limiting property and hence may be used as a promising dopant material. The study on concentration dependence of nonlinear optical parameters has been presented. © 2007 Elsevier Ltd. All rights reserved.Item Third-order nonlinear optical properties and two-photon absorption in polymers doped with p-phenyl sydnone(2008) Shettigar, S.; Umesh, G.; Chandrasekharan, K.; Rai, G.; Kalluraya, B.We report the measurements of the third-order susceptibilities and two-photon absorption in three different polymers doped with p-phenyl sydnone moiety viz., 2-benzylhydrazono-5-(3-p-tolylsydnone-4-yl)1,3,4,-thiadiazine, which is recently synthesized and characterized, with the prospective of reaching a good compromise between processability and high nonlinear optical properties. The measurements were done using nano second Z-scan at 532 nm. The Z-scan spectra reveal a large negative nonlinear refraction coefficient n 2 of the order 10-14 cm2/W and a two-photon absorption ?, which is determined to be the order of cm/GW. The absorption cross section is 10-46 cm4 s/photon. The molecular second-order hyperpolarizability in PMMA matrix was calculated to be 1.47 × 10-31 esu, comparable with stilbazolieum derivatives, a well-known class of optical materials for photonics and biophotonics applications. The chromophore shows its optical power limiting behavior in all the three polymer matrices. All these results suggest that this moiety has potential for the application of all-optical limiting and switching devices. © 2008 Wiley Periodicals, Inc.Item Fabrication of hair and copper fiber reinforced polymethyl methacrylate (pmma) composites and evaluation of their mechanical properties, thermal conductivity and color stability for dental applications(Society for Biomaterials and Artificial Organs - India sharmacp@sbaoi.org, 2016) Jayaprakash, K.; Nandish, B.T.; Rijesh, M.; Nayak, J.; Bhat, S.M.; Shetty, K.H.K.; Nityananda Shetty, A.; Prabhu, S.The objective of the work was to fabricate and evaluate the impact strength, flexural strength, thermal conductivity and color stability of heat cure Polymethyl methacrylate denture base resin, reinforced with human hair fibers and copper fibers. Specimens were prepared by reinforcing human hair fibers of 2mm length and diameter in the range of 64 -78 ?m, in different quantities with respect to two different age groups and genders, to polymer-monomer mix before dough stage. Same procedure was followed to fabricate specimens with copper fibers (2mm length and 200 ?m diameter) too. The impact strength, transverse strength, thermal conductivity, and color stabilities were measured by using standard equipment's. Scanning electron microscope (SEM) was used to study the fractured surface of the fiber reinforced composites. The impact strength increased three times in hair reinforced and about twice in copper reinforced composites. The transverse strength was slightly decreased and the cause for it was investigated. Copper fiber reinforced composite significantly increased the thermal conduction. The human hair and copper reinforced Polymethyl methacrylate showed significant improvements in its mechanical properties and retained color stability similar to control specimens during storage in various beverages.Item A facile synthesis of halloysite nanotubes based polymer nanocomposites for glass coating application(Elsevier Ltd, 2018) Buruga, K.; Kalathi, J.T.Halloysite-based polymethyl methacrylate (HNT-PMMA) and polystyrene (HNT-PS) nanocomposite coatings for glasses were synthesized by ultrasound-assisted solution blending method. The coatings were then dip-coated on four different types of soda-lime glass and the spectral, mechanical properties of the coated glasses were analyzed. The coated glass samples displayed a better scratch resistance and surface hydrophobicity, compared to uncoated samples, without any significant changes in their inherent spectral properties. The thermal and mechanical properties (Tg and tensile strength) of the nanocomposites were also enhanced compared to neat polymers. The improvement in thermal and scratch resistance of the coatings is ascribed to the inclusion of halloysite nanotubes (HNTs) in the polymer matrix. Hence, HNT-based PMMA/PS nanocomposite coatings can be effectively used for glasses in automotive and architectural applications. © 2017 Elsevier B.V.Item Synthesis of poly(styrene-co-methyl methacrylate) nanospheres by ultrasound-mediated Pickering nanoemulsion polymerization(Springer Netherlands rbk@louisiana.edu, 2019) Buruga, K.; Kalathi, J.T.Poly (styrene-co-methyl methacrylate) (PS-co-PMMA) nanospheres were synthesized by ultrasound-mediated Pickering nanoemulsion polymerization using halloysite nanotubes (HNTs) as a stabilizer. A relatively high conversion (? 99%) was obtained in a short span of time (60 min) relative to (?97%) for that obtained by conventional emulsion polymerization performed without ultrasound. The initial rate of polymerization and the conversion were found to be increasing with the acoustic intensity in the range of 12.5–25 W/cm2). The synthesized copolymer nanosphere particles exhibited a perfect spherical shape (from TEM analysis), good stability (from zeta-potential analysis), high molecular weight (Mw? 311 kDa from Gel permeation chromatography), and excellent thermal properties (Tg? 120°C from DSC and TGA) as a result of the combined physicochemical effects of acoustic cavitation. The formation of nanosized emulsion droplets stabilized by HNTs ultimately yielded nanospheres of PS-co-PMMA with an average size of ? 82.8 nm. The PS-co-PMMA nanospheres can have potential applications in medicine, dentistry, paper, paint, and automotive industries. © 2019, The Polymer Society, Taipei.Item Experimental investigation on performance of disposable micropump with retrofit piezo stack actuator for biomedical application(Springer Verlag service@springer.de, 2019) Mohith, S.; Karanth P, P.N.; Kulkarni, S.M.Extensive researches are being conducted to develop miniaturized pumping systems to fulfill the need for accurate delivery of fluids at required rates, particularly in the biomedical field. This paper presents the design, fabrication, and testing of novel valveless micropump actuated through an amplified piezo actuator. The proposed model of the micropump pump has the unique feature of a disposable chamber and employs low-cost polymeric materials, conventional molding and machining operations for fabrication. The disposable part of the pump consists of a laser-cut pump chamber with nozzle/diffuser made of Polymethyl methacrylate (PMMA) and conventionally molded silicone rubber diaphragm. The retrofit part includes the amplified piezo actuator and support structures build from PMMA. Systematic characterization of the pump was carried with water and blood mimicking fluid to understand the effect of operating parameters such as driving frequency and actuation voltage on flow rate and back pressure of the micropump. Experimental results show that the proposed design was capable of pumping 3.3–3.4 ml/min of dye solution and 1.7–1.75 ml/min of blood mimicking fluid at a driving frequency of 5 Hz and actuation voltage of 150 V. The corresponding computed volume resolution/stroke of the pump was found to about 5.75 µl and 11.25 µl of blood mimicking fluid and dye solution, respectively. The proposed pump was found to work effectively against a maximum back pressure of 156 Pa with blood mimicking fluid and 250 Pa with the dye solution as the working fluid under the same operating condition of 5 Hz and 150 V. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.